The Applied Study Of Multi-level Inverter In The Photovoltaic Generation System

The demanding of energy is growing day by day with the acceleration of economic globalization and the rapid development of industrial economy, as the energy consumption trend does not seem to be sustainable. This situation has led to research in renewable energies. As a clean and renewable green energy, the inexhaustible supply of solar energy is concerned by more and more people, and the technologies of exploring and utilizing has also been developing rapidly. The utilization of solar energy photovoltaic generation is a major way among them which is considered to be the most potential new energy technology in the world.The capacity of solar photovoltaic power station is continuously growing with the increasing popularity of solar photovoltaic. Solar photovoltaic energy is following its path in terms of installed power increase and applications. Improving the efficiency of electronic devices in photovoltaic system, reforming the output characteristics, and introducing these technologies into grid-connected, which become the important steps in the study of new energy generation technology. Therefore, multilevel Inverter technology is one of the most important methods in today's power generation technology.Higher power usually demands higher voltages, in order to maintain currents at an acceptable level. Isolation voltage limit of PV panels constrains the number of series-connected panels in a PV array, thus limiting its maximum DC voltage level. Therefore, multilevel inverters appear to be a very good solution for solar applications, as PV arrays concatenation is straight forward to each level of the DC link. In this scenario, power control of multilevel inverters for photovoltaic applications is recently being considered.In the photovoltaic generation system, we often connect several photovoltaic arrays in series with the conventional two-level inverter, the occurrence of partial shades and/or the mismatching of PVAs leads to a reduction of the power generated from its potential maximum. To overcome these problems, a method of connecting photovoltaic array with the diode clamped multi-level inverter is proposed in this paper. It is also presents a pulse-width modulation control technology to independently control each of the voltage in photovoltaic arrays. Compared to traditional two-level inverter system, this proposed method could maximize the system power which could reduce the rated voltage of equipments (better performance of the equipments'capability) and cut down the output voltage distortion, so the efficiency of the whole system is improved. Simulation and experimental tests have been conducted with three PVAs connected to a three-level three-phase diode-clamped converter to verify the good performance of the proposed system configuration and control strategy.